Maybe it's the time you went to that new upscale burger spot and one person ordered a burger, an app, the chocolate delight dessert and a wine that cost $16 a glass—then had two glasses. When the table's bill came? Yep, she split it evenly.

Or it was when an office buddy, without asking, started grabbing your french fries or putting their fork in your chocolate tart?

Did you stew? Did you gripe to the rest of your group? Well don't do that, says manners maven Patricia O'Brien. She has a few suggestions for such lunch-time irritants, including: Speak up!

What do you do when someone starts picking at your food without asking?

"If this is an every-time occurrence, it does get to be very aggravating. So what you might do is take the person aside and say, 'I wish you wouldn't do that'," says certified etiquette consultant O'Brien of Manners, Please. "Or you can just say, 'Here, why don't you just take the whole plate of french fries'."

And maybe, just maybe, she says, that might help them realize they shouldn't be doing that.

What do you do when you hate that everyone wants to share all the food?

"Sometimes this is a good idea because if you're eating in an ethnic-type restaurant, perhaps some of those (foods) are not something you would ordinarily order," she says. "But if you just really prefer not to share, you have to speak up immediately. You have to say something like, 'I really don't want to do that. I just prefer to order my own.' Speak up in the very beginning."

So what about the person always arrives late at the lunch?

"You can change the time for the person that's always late. So if you normally meet at 12, make it 11:45," she says. "And if that doesn't work, then this is one time that I would say you don't wait for them, you just start to order. … and perhaps they'll eventually get the idea."

Then must I stick around while they work their way through a platter of ribs?

"No, you can say, 'I have a time constraint here. I would really like to stay, but I can't.' And you can excuse yourself."

What about culinary inquisitors who ask why you don't eat or drinkpeanuts/wine/meat/bread/shellfish/beer?

"I would turn the question back by saying, 'Why do you ask?' And that might just stop them," she says. "If that doesn't work, you might say, 'Well, it's my personal choice.' And no futher answer is required."

And the check issue? You're OK with splitting the check equally if it's someone's birthday (or other special celebration), but when you get soup and salad at an everyday lunch while tablemates get lamb chops and prime rib?

"You have to speak up first and say 'Could we please have separate checks?' Usually a lot of the people at the table are relieved because they didn't have the courage to ask. Speaking up is probably the best thing you can do."

But I have to face these people again.

"So the next time the group is going out, say 'I'd really like to join you but I just can't participate in putting in extra money for food that I'm not eating.' Be upfront. People will probably respect you for that," says O'Brien. "You can say, 'Gee, I would really like to go, but can we go somewhere like Panera or something like that?' You've got to set the tone of where you're comfortable going. ...You don't need to tell people your personal problems. You don't hang the laundry out. You just say, 'I can't really do that today'."

And when we're at that fancy bistro and I want the $14 glass of wine while everyone else is getting sparkling water or a $6 house pour?

"You need to say to the the waitstaff person, 'I will pay for my wine separately.' Otherwise that's really very rude to order a glass of wine that costs that much when other people are having $6 or $8 glasses of wine."

Rest assured, if you use the wrong fork at lunch with co-workers, the earth won't open and swallow you up. That's a minor infraction in the great book of manners. O'Brien has seen a lot worse—a guy wearing a baseball cap in a white-tablecloth restaurant who used a linen napkin to blow his nose.